Extragalactic Astronomy and Cosmology

Peter Schneider
Argelander-Institut f. Astronomie
Univ. Bonn

On this page, I intend to put some additional material related to my textbook ``Extragalactic Astronomy and Cosmology. An introduction'' which appeared in October 2006 at Springer-Verlag. No attempt is made to be complete, nor homogeneous across the different chapters, nor systematic.

1. Introduction and overview
   1. Introduction
   2. Overview
      1. Our Milky Way as a galaxy
      2. The world of galaxies
      3. The Hubble expansion of the Universe
      4. Active galaxies and starburst galaxies
      5. Voids, clusters of galaxies, and dark matter
      6. World models and the thermal history of the Universe
         

         NEWS: The Nobel Prize in Physics 2006 was awarded to John Mather and George Smoot for their leadership of two ground-breaking experiments aboard NASA's Cosmic Background Explorer satellite. See the note written by Simon White for more information.

      7. Structure formation and galaxy evolution
      8. Cosmology as a triumph of the human mind
         

         A beautiful view to see how fully the sky is populated with galaxies, even in so-called empty fields, can be found here -- make sure to use the zoom-in facility

   3. The tools of extragalactic astronomy
      1. Radio telescopes
      2. Infrared telescopes
      3. Optical telescopes
      4. UV telescopes
      5. X-ray telescopes

         See the principle of an X-ray telescope, with XMM-Newton as specific example.

      6. Gamma-ray telescopes
   
   
2. The Milky Way as a galaxy
   1. Galactic coordinates
   2. Determination of distances within our Galaxy
      1. Trigonometric parallax

         The document Composition, Formation and Evolution of the Galaxy presents the science case for GAIA, and contains a lot of useful information on Galactic astronomy.

      2. Proper motions
      3. Moving cluster parallax
      4. Photometric distance; extinction and reddening
      5. Spectroscopic distance
      6. Distances of visual binary stars
      7. Distances of pulsating stars
   3. The structure of the Galaxy
      

      A view of the near-infrared sky as obtained from the 2MASS survey.

      1. The Galactic disk: Distribution of stars
      2. The Galactic disk: chemical composition and age
      3. The Galactic disk: dust and gas
      4. Cosmic rays
      5. The Galactic bulge
      6. The visible halo
      7. The distance to the Galactic center
   4. Kinematics of the Galaxy
      1. Determination of the velocity of the Sun
      2. The rotation curve of the Galaxy
   5. The Galactic microlensing effect: The quest for compact dark matter
      1. The gravitational lensing effect I
         

         An introduction to gravitational lensing can be found as part of my article Introduction to Gravitational Lensing and Cosmology A popular description of the lens effect can be found here

      2. Galactic microlensing effect
         

         An extended review on Galactic microlensing by Joachim Wambsganss can be found here

      3. Surveys and results
      4. Variations and extensions
   6. The Galactic center
      1. Where is the Galactic center?
      2. The central star cluster
      3. A black hole in the center of the Milky Way

         More information and illustrations of stellar motions around the Galactic Center can be found on the Web page "Galactic Center Research" of the group at MPE, Garching, including a movie of stellar orbits and a (possible) spin measurement of the black hole, as obtained from the observed flares.

      4. Flares from the Galactic center
      5. The proper motion of Sgr A*
      6. Hypervelocity stars in the Galaxy
   
   
3. The world of galaxies
   1. Classification
      1. Morphological classification: The Hubble sequence
         

         Images of Messier objects; in addition, this web site contains a detailed description of all Messier objects.

      2. Other types of galaxies
   2. Elliptical galaxies
      1. Classification
      2. Brightness profile
      3. Composition of elliptical galaxies
      4. Dynamics of elliptical galaxies
      5. Indicators of a complex evolution
   3. Spiral galaxies
      1. Trends in the sequence of spirals
         

         If you are hungry for images, you can find pictures of more than 600 spirals

      2. Brightness profile
      3. Rotation curves and dark matter
      4. Stellar populations and gas fraction
      5. Spiral structure
      6. Corona in spirals?
   4. Scaling relations
      1. The Tully-Fisher relation
      2. The Faber-Jackson relation
      3. The fundamental plane
      4. The Dn-sigma relation
   5. Black holes in the centers of galaxies
      1. The search for supermassive black holes

         If you are interested in black holes, you can get a journey through Black Holes: Gravity's Relentless Pull. This site also hosts a Black Hole Encyclopedia

      2. Examples for SMBHs in galaxies
      3. Correlation between SMBH mass and galaxy properties
   6. Extragalactic distance determination
      1. Distance of the LMC
      2. The Cepheid distance
      3. Secondary distance indicators
   7. Luminosity function of galaxies
      1. The Schechter luminosity function
      2. The bimodal color distribution of galaxies
   8. Galaxies as gravitational lenses
      1. The gravitational lens effect - Part II
      2. Simple models
      3. Examples for gravitational lenses
      4. Applications of the lens effect
   9. Population synthesis
      1. Model assumptions
      2. Evolutionary tracks in the HRD; integrated spectrum
      3. Color evolution
      4. Star formation history and galaxy colors
      5. Metallicity, dust, and HII regions
      6. Summary
      7. The spectra of galaxies
   10. Chemical evolution of galaxies
   
   
4. Cosmology I: Homogeneous isotropic world models
   1. Introduction and fundamental observations
      1. Fundamental cosmological observations
      2. Simple conclusions
   2. An expanding Universe
      1. Newtonian cosmology
      2. Kinematics of the Universe
      3. Dynamics of the expansion
      4. Modifications due to General Relativity
      5. The components of matter in the Universe
      6. ``Derivation'' of the expansion equation
      7. Discussion of the expansion equations
   3. Consequences of the Friedmann expansion
      1. The necessity of a Big Bang
      2. Redshift
      3. Distances in cosmology
      4. Special case: The Einstein-de Sitter model
      5. Summary
         

         You can find a Cosmology Calculator for the World Wide Web, made available by E.L. Wright (the description of the program is here). The program calculates, for given values of the density parameters, Hubble constant and redshift, the angular diameter distance, the luminosity distance, the age of the Universe, the comoving volume within the redshift, etc. For the more general situation of a Dark Energy equation of state more complicated that a cosmological constant, go to here.

   4. Thermal history of the Universe
      1. Expansion in the radiation-dominated phase
      2. Decoupling of neutrinos
      3. Pair annihilation
      4. Primordial nucleosynthesis
         

         Here you can find a comprehensive article by David Tytler, John M. O'Meara, Nao Suzuki and Dan Lubin on Big Bang nucleosynthesis

      5. Recombination
      6. Summary
   5. Achievements and problems of the standard model
      1. Achievements
      2. Problems of the standard model
      3. Extension of the standard model: inflation
   
   
5. Active galactic nuclei
   1. Introduction
      1. Brief history of AGNs

         You may want to read the nicely written Essay Quasar Astronomy Forty Years On by William Keel. In fact, Bill Keel's Web page on Quasars and Active Galactic Nuclei contains a lot of interesting material, figures and explanations.

      2. Fundamental properties of quasars
      3. Quasars as radio sources: synchrotron radiation
      4. Broad emission lines
   2. AGN zoology
      1. QSOs
      2. Seyfert galaxies
      3. Radio galaxies

         Alan Bridle's Gallery of Images of Radio Galaxies and Quasars features many impressive frames of radio AGNs.

      4. OVVs
      5. BL Lac objects
   3. The central engine: a black hole
      1. Why a black hole?
      2. Accretion
      3. Superluminal motion
      4. Further arguments for SMBHs
      5. A first mass estimate for the SMBH: the Eddington luminosity
   4. Components of an AGN
      1. The IR, optical, and UV-continuum
      2. The broad emission lines
      3. Narrow emission lines
      4. X-ray emission
      5. The host galaxy
      6. The black hole mass in AGNs
   5. Family relations of AGNs
      1. Unified models
      2. Beaming
      3. Beaming on large scales
      4. Jets at higher frequencies
   6. AGNs and cosmology
      1. The K-correction
      2. The luminosity function of QSOs
      3. Quasar absorption lines
   
   
6. Clusters and groups of galaxies
   1. The Local Group
      1. Phenomenology
         

         Find a List of Local Group Galaxies, together with a list of discoverers, images and information on individual objects. An informative and well illustrated Webpage on Local Group galaxies is also found here. It has become clear over the past few years that the census of galaxies in the Local Group is incomplete, as several new members of the Local Group have been discovered; see for instance the paper of Zucker et al. (2006).

      2. Mass estimate
      3. Other components of the Local Group
   2. Galaxies in clusters and groups
      1. The Abell catalog
      2. Luminosity function of cluster galaxies
      3. Morphological classification of clusters
      4. Spatial distribution of galaxies
      5. Dynamical mass of clusters
      6. Additional remarks on cluster dynamics
      7. Intergalactic stars in clusters of galaxies
      8. Galaxy groups
      9. The morphology-density relation
   3. X-ray radiation from clusters of galaxies
      1. General properties of the X-ray radiation
      2. Models of the X-ray emission
      3. Cooling flows
         

         The bullet cluster 1E 0657-56 presents arguably the best evidence for the presence of dark matter, in that alternative theories of gravity will find it very hard or impossible to explain the relative distribution of baryons (intracluster gas + stars in the galaxy) and matter, as seen from the weak lensing analysis, without referring to collisionless non-luminous matter. Check here for a press release and a pretty picture, and see the corresponding scientific publication by D. Clowe et al.

      4. The Sunyaev-Zeldovich effect
      5. X-ray catalogs of clusters
   4. Scaling relations for clusters of galaxies
      1. Mass-temperature relation
      2. Mass-velocity dispersion relation
      3. Mass-luminosity relation
      4. Near-infrared luminosity as mass indicator
   5. Clusters of galaxies as gravitational lenses
      1. Luminous arcs
      2. The weak gravitational lens effect
   6. Evolutionary effects
   
   
7. Cosmology II: Inhomogeneities in the Universe
   1. Introduction
   2. Gravitational instability
      1. Overview
      2. Linear perturbation theory
   3. Description of density fluctuations
      1. Correlation functions
      2. The power spectrum
   4. Evolution of density fluctuations
      1. The initial power spectrum
      2. Growth of density perturbations
   5. Non-linear structure evolution
      1. Model of spherical collapse
      2. Number density of dark matter halos
      3. Numerical simulations of structure formation
         

         If you want to read more about cosmological simulations of structure formation and galaxy formation and evolution, and see many more images and movies (including those of the currently largest N-body simulation, the Millennium Run), then visit the Web page of the Galaxy Formation Group at the Max-Planck Institut f. Astrophysik.

      4. Profile of dark matter halos
      5. The substructure problem
   6. Peculiar velocities
   7. Origin of the density fluctuations
   
   
8. Cosmology III: The cosmological parameters
   1. Redshift surveys of galaxies
      1. Introduction
      2. Redshift surveys

         The data of several major surveys become public after some proprietory period, and can then be accessed by everyone. For example, on the Web page of the Sloan Digital Sky Survey, one finds a description of the survey, images, publications -- but also available data, ranging from images, imaging catalogs, spectra, to redshifts for downloading. The same holds true for the 2dF Galaxy Redshift Survey.

      3. Determination of the power spectrum
      4. Effect of peculiar velocities
      5. Angular correlations of galaxies
      6. Cosmic peculiar velocities
   2. Cosmological parameters from clusters of galaxies
      1. Number density
      2. Mass-to-light ratio
      3. Baryon content
      4. The LSS of clusters of galaxies
   3. High-redshift supernovae and the cosmological constant
      1. Are SNIa standard candles?
      2. Observing SNeIa at high redshifts
      3. Results
      4. Discussion
   4. Cosmic shear
   5. Origin of the Lyman-alpha forest
      1. The homogeneous intergalactic medium
      2. Phenomenology of the Ly-alpha forest
      3. Models of the Ly-alpha forest
      4. The Ly-alpha forest as cosmological tool
   6. Angular fluctuations of the CMB
      1. Origin of the anisotropy: Overview
      2. Description of the CMB anisotropy
      3. The fluctuation spectrum
      4. Observations of the CMB anisotropy
      5. WMAP: Precision measurements of the CMB anisotropy
         

         In March 2006, the three-year data from WMAP have been published. On this webpage, you can find all the corresponding information, including an overview of the WMAP mission, links to the publications the accompany the data release, in particular the paper Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology by Davis Spergel et al. on cosmological implications of the data, temperature and polarization maps and much more. The three-year results confirm those from the first-year release, but the best-fit parameters change slightly (but within the confidence region obtained from WMAP-1). To quote from the Spergel et al. paper: "Using WMAP data only, the best fit values for cosmological parameters for the power-law flat LCDM model are (Omega_m h^2, Omega_b h^2, h, n_s, tau, sigma_8) = (0.127+0.007-0.013, 0.0223+0.0007-0.0009, 0.73 +- 0.03, 0.951+0.015-0.019, 0.09 +- 0.03, 0.74+0.05-0.06)."

   7. Cosmological parameters
      1. Cosmological parameters with WMAP
      2. Cosmic harmony
   
   
9. The Universe at high redshift
   1. Galaxies at high redshift
      1. Lyman-break galaxies (LBGs)
      2. Photometric redshift
      3. Hubble Deep Field(s)

         More details on the Hubble Ultra Deep Field can be found at this press release, where also many additional images can be found. And here you find the technical description -- the HUDF release paper by Beckwith et al.

      4. Natural telescopes
   2. New types of galaxies
      1. Starburst galaxies
      2. Extremely Red Objects (EROs)
      3. Submillimeter sources: A view through thick dust
      4. Damped Lyman-alpha systems
      5. Lyman-alpha blobs
   3. Background radiation at smaller wavelengths
      1. The IR background
      2. The X-ray background
   4. Reionization of the Universe
      1. The first stars

         Find extended reviews on "First Light" by Abraham Loeb and "The First Cosmic Structures and Their Effects" by Benedetta Ciardi and Andrea Ferrara

      2. The reionization process
   5. The cosmic star-formation history
      1. Indicators of star formation
      2. Redshift dependence of the star formation: The Madau diagram
   6. Galaxy formation and evolution
      1. Expectations from structure formation
      2. Formation of elliptical galaxies
      3. Semi-analytic models
      4. Cosmic downsizing
   7. Gamma-ray bursts
   
   
10. Outlook

    Great news: On Oct.31, 2006, NASA Administrator Michael Griffin announced plans for a fifth servicing mission to Hubble. During this servicing mission, new gyros and batteries will be installed, which will extend Hubble's lifetime presumably until 2013. In addition, with the installemnt of two new powerful instruments, the capabilities of the HST will be strongly enhanced.

    
    

    If you want to read more about the future, or at least what other people think the future of astrophysics and science will bring, here are a few interesting documents to look at: The Cosmic Vision 2015-2025 of the European Space Agency (ESA) outlines the ideas and visions for a European Space Program in next 20 years; a well-made and very interesting document on the future of our field. The Report of the Dark Energy Task Force has been released; it describes the future avenue toward astrophysical research on dark energy, comparing various techniques and potential facilities on how to contrain the properties of dark energy. In particular, it also contains a `Dark Energy Primer', plus many many more useful items. Report of the ESA/ESO Working Group on Fundamental Cosmology, a 120 page booklet analyzing the main science questions of this topic, and giving recommendations for future projects to solve (some of) them. Then there are a number of national decadel reviews where the future of astrophysics in these countries are considered, e.g. The UK PPARC published the Roadmap